In power supply industry, indicators for a power module, in particular for a power converter include high efficiency, high power density and high reliability. Then high efficiency means reduction of energy consumption, which is beneficial to energy conservation and emission reduction, as well as environment protection and reduction in use cost. The high power density means small volume and light weight, which could bring reduction in transportation cost and space requirement, thus leading to reduction in construction cost. Higher reliability is accompanied by longer service life and lower maintenance cost.
The above three indicators sought by the industry are closely linked with good thermal management. Firstly, at a lower operating temperature, conduction losses of a power module (e.g., Metal-Oxide-Semiconductor Field-Effect Transistor, MOSFET) may be reduced, which is beneficial to improving system efficiency.
Secondly, on many occasions, heat generated by a power device may directly influence its power density. Taking a power converter for an example, semiconductor devices therein typically have relatively large energy consumption. Therefore, the semiconductor devices may be considered as one of the most important factors determining efficiency of the power converter. Moreover, tolerable temperature of a semiconductor device has a certain limit, and the semiconductor device may be deteriorated sharply in performance or even disabled when the limit is exceeded. Therefore, it is vital important to provide a high-efficiency heat dissipating system capable of keeping temperature of a semiconductor chip within an acceptable range.
Thirdly, lifespan of the semiconductor device is also closely associated with the working temperature. A relatively lower operating temperature may enable a longer service life of the semiconductor device. Generally, there is such an engineering empirical rule in the electronic field that the lifespan of the device may be shortened by half for each 10° C. rise of the temperature. As can be known from above, the good thermal management is of critical importance in improving conversion efficiency, power density and reliability of the device.
Now, taking an example of a semiconductor device using DBC (Direct Bonded Copper) ceramic substrate as substrate, as shown in FIG. 1, a power device (chip) 1 is mounted on a substrate 2 by die bonding material, and electric, mechanical and thermal connections between the power device 1 and traces (not shown in FIG. 1) of the substrate is realized by the die bonding material. An area of upper surface of the power device 1 is covered with a molding component, so as to achieve protection in aspects of mechanical, anti-dust, moisture proof and insulation. Typically, a heatsink 3 is mounted on a lower surface of the power device 1, since heat generated by the power device 1 may be transferred mainly via the lower surface of chip to the bottom side of the substrate 2, thereby forming a relatively good channel for heat transfer. The heatsink 3 may be made from material with a relatively high thermal conductivity, for example, copper, which has a thermal conductivity above 300 W/m·K. In order to ensure a good heat conduction path between the lower surface of the power device 1 and the surface of the heatsink 3, thermal interface material such as heat-conducting silicone grease 4 may be applied therebetween. The heat-conducting silicone grease 4 is filled in gaps between the power device 1 and the heatsink 3, thus realizing a better heat conduction than air. In addition, in order to facilitate users to install a heatsink, a spring clip 5 is provided for realizing mechanical fixation between the power device 1 and the heatsink 3.
The foregoing information is merely disclosed to facilitate understanding of background of the present disclosure. Therefore, the foregoing information may include information not constituting the prior art known to those of ordinary skill in the art.